This invention relates to the field of conducting organic polymers, and particularly to a conducting organic polymer which is electrochemically deposited on a cathode.
Within the last several years, polymers have been discovered which have high electrical conductivity. Although there are many potential applications for conducting polymers, their use has been thwarted by chemical instability, poor mechanical properties, difficult fabricability, and/or the inability to apply them to suitable substrate materials.
Both chemical precipitation and electrochemical methods have been used to produce conductive polymers. In the prior art electrochemical methods, a conducting polymer, such as polypyrrole, is deposited on an anode from an electrolyte. See for example "Electrochemistry of Conducting Polypyrrole Films" by A. F. Diaz in the Journal of Electroanalytical Chemistry, 129, (1981), pp. 115-132. Anode materials in these cases are limited to noble metals and to a few stable semiconductors which do not themselves oxidize (or dissolve) during the deposition process. Consequently, prior art substrates for electrochemically-produced polymers were limited to these few anode materials.
Chemical precipitation has also been used to produce conducting polymers based upon transition metal ion-bridged tetrathiooxalate (C.sub.2 S.sub.4.sup.2-, or TTO.sup.2-) liquids derived from the two-electron reduction of carbon disulfide. These polymers, prepared from the reaction of TTO.sup.2- with nickel, copper, or palladium (2+) salts, appear to consist of short chain oligomers having about three metal atoms, four TTO anions, and one cation (Et.sub.4 N.sup.+). They have conductivity values of up to 20 (ohm-cm).sup.-1. This chemical precipitation process is described by J. R. Reynolds et al in an article titled "Electrically Conducting Transition Metal Complexes of Tetrathio-oxalate", in the Journal of the Chemical Society, Chemical Communications, 1985, pp. 268-269.
There is a continuing need for new conducting polymers having higher structural order and higher conductivities; and for new methods of forming these polymers so that coherent thin films can be formed on a wide variety of cathode substrates rather than upon only substrates which are suitable for anodes in electrochemical processes.